The present invention relates generally to a machine for cleaning articles, more particularly to a machine having a system for reducing the amount of energy and water consumed during an operation cycle.
Reducing the amount of energy and water consumption in appliances such as dishwashers or clothes washers, is a significant problem, in part because a large amount of energy is needed to heat incoming water. For example, dishwashers use energy from two distinct sources. One source is the water-heating energy (WHE) consumed by the hot water heater that supplies hot water to the dishwasher. The second source is the electrical energy used to run the dishwasher pump and a resistance heating element enclosed in the dishwasher. The resistance heating element boosts the water temperature during wash and dries the dishes after they are clean.
The Department of Energy (DOE) requires manufacturers to measure the mechanical energy consumed by the motor and heating element with a kilowatt-hour meter and the quantity of water used with a flow meter and timer. The total energy consumption per cycle is defined as E=WHE+M, where WHE is the water heating energy used by the hot water heater to supply hot water to the dishwasher and M is the mechanical energy consumed by the motor and heating element, that is measured with the kilowatt-hour meter. Incoming 120.degree. F. hot water is assumed to be provided from a 50.degree. F. cold source with a constant volumetric specific heat (Cv) of Cv=0.00240 kwh/gal- .degree. F. The "Normal" cycle of a typical dishwasher uses a volume (V) of water for an entire cycle of V=9.1 gallons.
The equation for Water Heating Energy (WHE) is WHE=V Cv (T.sub.2 -T.sub.1), where T.sub.2 is the temperature of the heated water and T.sub.1 is the temperature of the water from the cold source. Therefore, the WHE for one cycle is 9.1 gal.times.0.0024 kwh/gal- F.times.70F=1.5288 kwh of water heating energy. The average mechanical energy consumption per cycle runs about 0.65 kwh. From Equation 1, the average total energy consumption for a "Normal" cycle is 2.1768 kwh. Therefore, reducing the water heating energy by reducing the water consumption has a major impact on the overall energy consumption of the dishwasher.
As stated above, the DOE energy rating for the dishwashers is based primarily on the amount of hot water consumed to complete the washing of one load. Most dishwashers presently require about 9.1 gallons of hot water per load. Each load requires about six (6) fills of fresh hot water, about 1.4 to about 1.9 gallons of hot water per fill. The first two fills are needed for the prewash cycles, followed by a fresh fill for the main wash cycles. The last three fills are needed for the two post rinse and one final rinse cycle. Based on six (6) fills (9.1 gallons of water), the DOE rating is about $59.00.
Prior efforts to recycle hot water from one fill to the next have usually involved the use of a screen (coarse or fine) and the use of a centrifuge to separate the soils. The screens often need to be removed and cleaned to prevent bacteria growth, and are, thus, inefficient and impractical. The centrifuge is efficient, but it has to be rotating at all times to provide efficient separation, which requires energy and the moving parts require more space and more maintenance.
Therefore, it is apparent from above that there exists a need in the art for reducing the energy consumption during wash loads of cleaning machines, such as dishwashers. Such systems and methods should at least partially recycle the water during a fill or reuse at least a portion of the same hot water from one cycle to another, thereby, achieving significant energy saving. For the hot water to be recycled or reused, it has to be separated from particles and any suspended or dissolved solids. It is a purpose of this invention, to fulfill these and other needs in the art in a manner more apparent to the skilled artisan once given the following disclosure.